1. Technical Field
The technology described in this patent application is generally directed to the field of unipolar generators. More specifically, a resonant unipolar generator is described that is capable of supplying megawatt AC power for a variety of applications heretofore unrealized due to the absence of a suitable power source.
2. Description of the Related Art
Conventional AC electric generators operate at a frequency determined by the number of poles and the shaft rotational speed. The frequency of electric power generated by such generators is limited by mechanical constraints to a few kHz at most. Higher frequency operation can be produced by electronic solid-state or vacuum tube switching devices, or alternatively with a resonant cavity. Such electronic methods, while capable of high frequency, however, are restricted to relatively low power levels in the kilowatt range. Production of electricity at both high frequency (mHz) and high power (megawatts) is heretofore unrealized using conventional power generation technology.
Conversion of electric power to mechanical shaft power was first demonstrated by Michael Faraday in the early 1800s in the form of a unipolar (or homopolar) motor. It is the only electrical/mechanical conversion device that is fundamentally DC in nature. All other so-called DC machines are in fact AC machines requiring commutation or rectification of some sort to change the inherent AC to DC. DC power from a unipolar machine is not easily transformed to high voltage/low current for long distance transmission, and the single-turn unipolar format cannot directly generate the standard current and voltage characteristic required for economic power distribution. Consequently, the unipolar motor/generator developed by Faraday has remained largely a laboratory curiosity except in highly specialized applications, such as electrolytic metals refining where low voltage and high DC current are required.
The multi-turn AC motor/generator has enjoyed commercial success from its introduction due to its desirable AC input/output and favorable voltage/current characteristics. Shaft frequency (i.e., rotational speed) of this and all AC machines is essentially synchronous with electrical frequency. The electrical frequency is typically a multiple of shaft frequency where the multiple is determined by the number of pole pairs physically existing in the machine. Obtaining higher frequency for a given shaft speed in this type of AC machine involves increasing the number of poles. A practical limit in both rotational speed and the number of poles thus determines the maximum electrical frequency obtainable from such an AC machine.
By contrast, there is no relationship between electrical frequency and shaft speed in a unipolar machine simply because, being intrinsically DC in nature, there is no frequency to begin with. However, it is possible to impart AC properties in the unipolar format while still retaining the unique independence of shaft and electrical frequencies. In short, the unipolar principle permits electrical frequencies transcending the mechanical limitations found in standard AC machines.
As with all rotating electrical apparatus, shaft torque is a function of the algebraic product of current and magnetic field. If both current and field reverse simultaneously, than the shaft torque remains unidirectional. This same principle is found in the common series-wound, mechanically-commutated “universal” motor found in small appliances, such as vacuum cleaners, blenders, etc., which explains why this type of motor is able to run at speeds unrestricted by the number of poles as explained above. Because shaft speed is not synchronous with the input frequency, efficiency of the universal motor is poor, relegating it to fractional horsepower applications.
The unipolar format, by comparison, has no criteria for shaft/electrical synchronicity, which renders it suitable for high horsepower applications. Similar to the universal motor, the unipolar rotor circuit is connected in series with the stator field coil (exciter), assuring shaft torque produced by interaction of rotor current and stator field is continuous in one direction only. The standard unipolar motor/generator, however, suffers from a high current/low voltage characteristic. Typically, thousands of amps must be conducted onto the perimeter of the rotor where the surface velocity is maximum using mechanical slip-rings and brushes. Surface wear resulting from mechanical friction and localized arcing accompanied by contact voltage drop are problems that have never been satisfactorily solved. To raise the voltage to more practical levels, the rotor speed must be as high as possible, which compounds the sip-ring conduction problem. Another problem with this configuration is the high current/low voltage DC input/output, which is not amenable to transformer modification because transformers are strictly AC devices.